He was Called to the Bar in 1968 and took Silk in 1982. In 1993, he was appointed a deputy high court judge, in 1997 he became a high court judge and, in 2009, he was made a Lord Justice of Appeal.

Lord Justice Sullivan  has specialised in administrative law throughout his career. He has been involved in several high-profile cases as a judge, including the 2006 Afghan hijackers case, where he ordered that the hijackers be given discretionary leave to remain, and the 2007 Greenpeace case on nuclear energy, where he ruled the government had been ‘misleading’ in its handling of the debate.